Atherosclerosis is a chronic inflammatory disease of the arterial vessel wall that progresses from a fatty streak to a fibrofattymatrix and fibrous plaque. Monocyte interactions with the inflamed endothelium, monocyte recruitment to the arterial vesselwall and their subsequent transformation to lipid-enriched foam cells initiate and sustain atherosclerosis. The long-term goal of this research project is to elucidate the mechanisms underlying the regulation of the inflammatory aspects of atherosclerosis so that novel evidence-based approaches can be developed to treat atherosclerosis. The central hypothesis of this proposal is that suppressing adenosine kinase (ADK) inhibits the inflammatory aspects of atherosclerosis and further curbs the formation of atherosclerotic lesions. Adenosine, a purine nucleoside that is elaborated the sites of inflammation, has a central role in regulating the inflammatory response. However, the short half-life and systemic side effects of adenosine or adenosine analogues limit their application. ADK is an intracellular enzyme that catalyzes the phosphorylation of adenosine to AMP. Inhibition of ADK increases the levels of adenosine in the intracellular compartment and causes a subsequent increase in the extracellular compartment. ADK inhibition is efficacious at suppressing many inflammatory diseases in animal models. However, the role of ADK inhibition in atherosclerosis has not been defined. We have recently found the following: (i) an ADK inhibitor suppresses the formation of atherosclerotic lesions in mice; (ii) ADK knockdown in endothelial cells decreases cytokine-induced endothelial activation; and (iii) the deficiency of ADK in myeloid leukocytes reduces the formation of atherosclerotic lesions in mice. The goal of this project is to use tissue- specific ADK-deficient mice to investigate the extent to which ADK deficiency in endothelial cells or monocytes/macrophages contributes to the reduction of inflammatory responses and the suppression of atherosclerosis. In specific aim 1, we will investigate the effect of endothelial ADK deficiency on the decreased inflammatory adhesiveness of the arterial endothelium and the suppressed formation of atherosclerotic lesions. In specific aims 2 to 4, we will investigate the effects of monocyte ADK deficiency on the decline of monocyte recruitment to atherosclerotic arteries, macrophage activation and foam cell formation, as well as the growth of advanced atherosclerotic lesions. We will also determine the contribution of the PI3K/Akt and adenosine receptor 2A (A2AR) to the effects of ADK deficiency. These studies will have significant implications for the use of ADK inhibitors as therapeutic agents to prevent and treat atherosclerosis and its complications.